In the semiconductor industry, chemical-mechanical polishing (CMP) is used to remove a portion of a film deposited on a wafer. In a CMP process, a film is selectively removed from a semiconductor wafer by rotating the wafer against a polishing pad (or rotating the pad against the wafer, or both) with a controlled amount of pressure in the presence of a slurry.
Monitoring and controlling the CMP process is difficult, since many different factors influence the polishing rate (e.g. rotation speed, polishing pad wear, chemical reactions between the slurry and the wafer surface, etc.). It is desirable to (1) detect when polishing should be stopped (i.e. when the process endpoint has been reached), (2) detect particles in the slurry which cause scratching, (3) detect chemical species for contamination control, and (4) understand the process chemistry. Such tasks could be performed by in-situ real time (i.e. while the wafer is being polished) slurry sampling and analysis. This requires a robust collection apparatus which is not affected by the slurry chemistry, does not interfere with the polishing, and enables sampling with a rapid response time.